فصلنامه رویکردهای نوین در مهندسی عمران
سال هفتم شماره 4 (زمستان 1402)

In engineering design methods, it is assumed that the structure is located on a fixed base, and the effects of the soil environment on the structural response are generally ignored. However, research showed that the environment of the soil and the structure can interact with each other. This phenomenon is called soil-structure interaction effect. Therefore, the soil environment should be modeled in structural analysis. There are different methods for soil modeling. One of the practical methods is to use separate springs to model the soil environment. In this article, the effect of the number of floors and the period of the structure on the soil springs’ stiffness has been investigated. In this regard, three-dimensional structures with the number of floors 1, 3, 5 ,10 and 15 were modeled in Opensees software with continuous soil environment. Then, from the results of the structural analysis, the reaction of the soil under the foundation was calculated and relations were presented to determine the stiffness of the soil. These relationships are dependent on the structure’s period.

For various reasons, such as lack of suitable land or architectural considerations, engineers may construct the foundation adjacent to or inside the slope body. Therefore, the problem of the bearing capacity of strip foundations placed on the slope and the safety factor of these slopes has been the focus of many researchers. On the other hand, especially in urban environments, the possibility of foundations being placed adjacent to each other is very high, and for this reason, the interference effect of nearby foundations is another challenge that researchers have investigated. In this research, these two challenges have been integrated and the interference effect of adjacent foundations placed on the body of the slope has been investigated using PLAXIS finite element software. In this way, one foundation is attached to the upper edge of the slope and the other foundation is considered inside the body of the slope. The parameters examined in this study are slope angle, slope length, soil friction angle, and soil cohesion. All of these parameters have been studied in the case of single footing and two interfering footings. The results indicate that an increase in the angle and length of the slope causes a decrease in the bearing capacity of the footing and a decrease in the safety factor of the slope. Also, with the increase of cohesion and friction angle, the bearing capacity of the footing and the safety factor of the slope increased. The interference effect caused an increase in the bearing capacity and a decrease in the safety factor, and by increasing the length of the slope more than 5B at different angles of the slope, the interference effect disappeared.

The vital infrastructures of a city are a set of networks and systems, in the absence of any of them, the functioning of the city and the provision of basic services needed for life will face problems. In the event of an accident, the performance of these components and networks, including the network Electricity, water, transportation, telecommunications and gas, and the demand for their use will be affected, and the failure and lack of each network will affect the performance of other networks. These networks should be looked at from the point of view of a system of systems, in the current research, the components of 5 electricity, water, gas, telecommunication and transportation networks have been examined and the components have been specified in the form of a table, at the end of the evaluation The performance of the infrastructures in the event of an earthquake has been studied and it has been concluded that in the event of an earthquake, the probability of damage is what it looks like according to the extent and concentration of the infrastructures and the costs of reconstruction and the duration of the repair. The initiative of this research is the attitude towards infrastructures It is in the form of categorizing and presenting new tables, such as the tables of each infrastructure separately and aggregating the infrastructure in one table and checking their status and vulnerability at the same time.

Population growth in most cities has increased the need to implement surface and subsurface infrastructure. Tunneling causes changes in surface and subsurface structures. On the other hand, the existence of structures also affect the displacements of the ground due to tunneling. Therefore, investigating and estimating the interaction between the tunnel and the surface structures, in terms of the effect that the presence of the surface structures has on the amount of settlement and displacements caused by tunneling, is of particular importance. In recent decades, researchers have conducted their studies focusing on various factors. In this article, an attempt has been made to investigate the influence of the parameter of the distance between the center of gravity of the structure and the tunnel diameter (X/D) on the settlement and displacement curves of the ground surface due to tunnel excavation. For this purpose, finite element numerical method (FEM) has been used. Based on the results of numerical modeling, the amount of settlement has been reduced by reducing the X/D ratio. Also, by reducing this ratio, the impact range of the settlement also decreases. Changes in the X/D ratio do not have much effect on the longitudinal settlement curve above the tunnel axis, but with the decrease of the X/D ratio below the center of gravity of the structure, the maximum longitudinal settlement increases. Also, by reducing the X/D ratio, the amount of horizontal displacements will increase.

Concrete is the most used construction material in the world. Today, there are various concretes with different applications in the industry. One of the types of concrete is fiber concrete. In this study, several concrete samples were made with steel, glass and polypropylene fibers and the effect of the volume and weight percentages of each of the fibers in improving the compressive strength of the samples at temperatures Different has been checked. In order to check the results and the possibility of comparing it with the behavior of normal concrete, a type of concrete without fibers was also made using common materials and similar tests were performed on it. Based on the investigations, the results showed that the concrete samples with steel fibers tolerated higher temperature levels and had higher resistance compared to other samples. In the samples, by adding 0.25% and 0.5% by volume of steel fibers to concrete, respectively, the compressive strength of the sample at high temperatures was improved. The strength of concrete samples with 3400 Kg/m was slightly decreased by increasing the percentage of fibers from 0.5% to 0.75%. The compressive strength of concrete containing steel fibers is 20% higher than that of concrete containing propylene fibers.